Why Might One Expect the Public Sector to Pay Lower

Why might one expect the public sector to pay lower wages, ceteris paribus, than the private sector?

A) Public sector workers tend to have a higher degree of job security.
B) The skills and education levels of these workers is lower than that of their private sector counterparts.
C) The demand for labour in the public sector is often quite wage inelastic.
D) Public sector workers are less heavily unionized than their private sector counterparts.
E) Public sector workers have less fringe benefits than their private sector counterparts.